How can I run host code on KV260 without using xmutil before?

I m following the tutorial Vitis_Platform_Creation/Design_Tutorials/01-Edge-KV260/step3.md and i finally TEST PASSED. But I have met 2 problems: When I try ed to run host code without using xmbutil before, linux os will collapse. Then I tried to run  `xmbutil unloadapp` and xmbutil loadapp ＜any app＞, xmbutil will stuck in python at a function call which named "waitpid".